Some of Hollywood's biggest names have been open about their love for the planet. So in honor of Earth Day, MTV News zeroed in on some of La La Land's greenest superstars to show the ways in which they're using their celebrity to shed light on important environmental causes.

Leonardo DiCaprio has set the bar very high for other green celebs. And he is, in many ways, the face of environmentally-minded Hollywood. Not only does he have his own foundation focused on finding sustainable options, but he also wrote, produced, and narrated "The 11th Hour," a film about the dangers of global warming.

Much like DiCaprio, Ed Norton is a well-known activist who has worked with charities that help bring attention to Mother Earth. Norton has also teamed up with the Enterprise Green Communities Initiative and BP's Solar Neighbors program. He recently worked with Joe Jonas for the singer's Change for the Children Foundation.

Joe has been vocal about the ways his fans can help the planet. Last year, he recorded the song "Make a Wave" for the "Oceans" soundtrack, and he spoke MTV News about getting involved.

"There [are] a lot of things that people can do to help out that they don't really know about. The movie really ... helps you understand what you can do. Whether it's really taking your time and going to the beaches and helping out or whether it's something at home, there's so many different things that if we all do it together, just like anything else, we can make a big impact."

Alicia Silverstone, a vegan, continues to spread the word about eating sustainable foods. She released a cookbook, "The Kind Diet," and shared with MTV News why she feels it's important others eat in a way that's both "kind" to the environment and their own bodies.

"I started to glow, and people were like, 'Why do you look so great?' I felt so much better, and I used to take an asthma inhaler and I used to get allergy shots — and all that stuff went away. And my skin got great," she explained. "So what I found was at first, I thought this was good karma."